1. Field of the Invention
The invention relates primarily to the field of color, flat-panel display devices.
2. Description of Related Art
The prior art contains various approaches to the problem of providing color, flat-panel displays. A common approach is to form a pixel of a plurality of color cells. One such approach, using liquid crystal, utilizes three color cells--one red, one green, and one blue--to form an RGB (red-green-blue) pixel. This is sometimes modified to include a fourth cell for control purposes. Another similar approach includes a color plasma pixel comprised of nine color cells. The bottom three cells are blanks inserted to prevent smearing of the image due to locally intense electrical effects native to the plasma approach.
The underlying principle of such conventional color pixels relies on the physiological fact that the color cells making up the respective pixels are too small to be individually resolved am a spatial matrix of separate colors. This optical limitation of human vision means that the eye integrates each of the separate colors from a pixel and perceives them as a mixture. Thus such prior art pixels exploit the eye's tendency to integrate details on a sufficiently small spatial scale. However, human vision is limited not only with respect to spatial resolution, but also with respect to temporal resolution. The limited temporal resolution of human vision (which gives rise to the effect known as persistence of vision) allows humans to see motion pictures as continuous moving images rather than as the consecutive still images they actually are. This temporal-integrative attribute of human vision is utilized in the present invention. It is thus an object of the present invention to provide an improved pixel which, in conjunction with other aspects of the present invention, is yet able to provide color as well as black-and-white display.
Generally the prior art approaches utilize one of the following types of pixels: color liquid crystal; color gas plasma; color electroluminescent; and electrochromic. Each of these approaches exhibits serious disadvantages. For instance, liquid crystal display screens often exhibit the following disadvantages: directionality limits off-axis viewing; demands considerable backlighting power; sustains optical losses due to color filtering intrinsic to the approach; flexible backlights hove short product lives (less than 5000 hours); environmentally limited by the liquid crystal freeze point. Color plasma screens often exhibit these disadvantages: uses secondary emission process (excitation of neon causes color phosphor to radiate); containment of noble gas presents packaging constraints (rigid glass screens are required); unlike black-and-white plasma, color pixel life is short; extremely high manufacturing costs; very high power drain, especially when energized to sunlight-readable viewing levels. Finally, electroluminescent and other approaches often exhibit these disadvantages: key colors are presently elusive in electroluminescent technology, and display life is unacceptably short; certain electroluminescent embodiments are power-hungry; electrochromic and similar organic approaches have been discredited in the information display community.
Particularly when considering military or environmentally difficult applications, the foregoing prior art approaches quickly manifest their deficiencies. They are lacking chiefly the following characteristics which are necessary for these applications: no susceptibility to thermal environmental factors (this rules out liquid crystals); long display life (this rules out phosphors and electroluminescence); lower power consumption (a likely consequence of a low optical loss design); attains theoretical limits for pixel color generation and electronic control; intrinsically easy to ruggedize.
Thus, among the objects of the present invention, are the following: avoid filtration to prevent optical losses; avoid secondary emissive effects to prevent additional loss of efficiency; avoid existing light-generative means employed by prior art flat panel technologies; and to provide an improved pixel.
Among specific prior art display devices are the following. Simpson et al. U.S. Pat. No. 4,794,370 discloses a display device wherein electrostatic force is used to position a flexible member in relation to a stator member in order to achieve an array of binary elements suitable for alphanumeric or graphic displays. Veenvliet et al. U.S. Pat. No. 4,807,967 discloses a device wherein a movable electrode is propelled between two stationary electrodes by (at least in part) electrostatic force and (in at least one embodiment) a mechanical spring force. An opaque, non-conductive liquid disposed between the stationary electrodes provides the optical characters depending on the position of the movable electrode. Todd et al. U.S. Pat. No. 4,234,245 discloses an arrangement wherein a bimorph element comprised of ceramic piezoelectric material is electrostatically bent between first and second positions in order to shutter light. Generally the prior art devices, as the foregoing, to the extent they may be relevant to the instant area of invention, are undesirably slow and lacking in optical resolution.